Inks, such as ink jet inks, often utilize dyes as colorants because of their high chroma, brightness, and transparency. Dyes, however, present some durability disadvantages, particularly in the water-based inks commonly employed in consumer and commercial ink jet printers. Such dyes are typically water-soluble and consequently exhibit poor print waterfastness and poor bleed control when printed next to other colors or subsequently subjected to humid conditions. Such dyes also typically have poor lightfastness and fade at different rates, depending on the color.
More recently, the ink jet ink industry has employed dispersed pigment colorants in place of dyes. The pigments are often aggregated particles comprising, for example, metal oxides or organic materials. As such, pigments typically have greater waterfastness, bleed resistance, and media-independent color properties over conventional dyes. Moreover, pigments typically exhibit far superior photo-stability than dyes. As with aggregated colorants in general, however, pigments typically exhibit a noticeable reduction in chroma and brilliance as compared to dyes. Pigments also typically have poor transparency, such that overprinted colors tend to mask underprinted colors.
As a result, it would be desirable to provide a commercially viable, readily manufacturable, pigment containing ink composition, such as an ink jet ink composition, that can exhibit the color properties of a dye based ink composition (chroma, brilliance, transparency), while maintaining the durability properties (lightfastness, waterfastness, and humidity resistance) of a pigment based ink composition. It would also be desirable to provide such ink compositions that can exhibit excellent storage stability.